introduce external services

loader/loader_test.go

@@ -3760,3 +3760,20 @@ services:
 	assert.Equal(t, len(p.Services["test"].Secrets), 1)
 	assert.Equal(t, *p.Services["test"].Secrets[0].Mode, types.FileMode(0o440))
 }
+
+func TestExternalService(t *testing.T) {
+	p, err := loadYAML(`
+name: external-service
+services:
+  test:
+    external:
+      type: foo
+      options:
+        bar: zot
+`)
+	assert.NilError(t, err)
+	assert.DeepEqual(t, p.Services["test"].External, &types.ExternalServiceConfig{
+		Type:    "foo",
+		Options: map[string]string{"bar": "zot"},
+	})
+}

loader/validate.go

@@ -29,7 +29,7 @@ import (
 // checkConsistency validate a compose model is consistent
 func checkConsistency(project *types.Project) error { //nolint:gocyclo
 	for name, s := range project.Services {
-		if s.Build == nil && s.Image == "" {
+		if s.Build == nil && s.Image == "" && s.External == nil {
 			return fmt.Errorf("service %q has neither an image nor a build context specified: %w", s.Name, errdefs.ErrInvalid)
 		}
 

schema/compose-spec.json

@@ -259,6 +259,20 @@
             }
           ]
         },
+        "external": {
+          "type": "object",
+          "properties": {
+            "type": {"type": "string"},
+            "options": {
+              "type": "object",
+              "patternProperties": {
+                "^.+$": {"type": ["string", "number", "null"]}
+              }
+            }
+          },
+          "additionalProperties": false,
+          "patternProperties": {"^x-": {}}
+        },
         "external_links": {"type": "array", "items": {"type": "string"}, "uniqueItems": true},
         "extra_hosts": {"$ref": "#/definitions/extra_hosts"},
         "gpus": {"$ref": "#/definitions/gpus"},
@@ -279,7 +293,6 @@
         "links": {"type": "array", "items": {"type": "string"}, "uniqueItems": true},
         "logging": {
           "type": "object",
-
           "properties": {
             "driver": {"type": "string"},
             "options": {